+**Phlegm** is a thick, viscous [Mucus](/wiki/mucus) produced by the [Respiratory System](/wiki/respiratory_system). It acts as a protective agent, trapping irritants and pathogens to be expelled from the body.
+## See also
+- [Cough](/wiki/cough)
+- [Sputum](/wiki/sputum)
+- [Bronchitis](/wiki/bronchitis)
... 1 more lines